Stable Cycling of High‐Voltage Ni‐Rich Lithium Metal Batteries through Solvation Structure Regulation by Functional Electrolyte Co‐Additives

Abstract Ether‐based electrolytes with exceptional lithium metal compatibility and low‐temperature performance are expected to be the alternative to conventional ester‐based electrolytes for next‐generation lithium metal batteries. However, the poor oxidation stability of ether solvent (<4.0 V vs Li + /Li) with high‐voltage cathode materials prevents their further application. Herein, a localized high concentration electrolyte approach is demonstrated based on the simultaneous introduction of fluoroethylene carbonate and lithium nitrate (LiNO 3 ) as synergistic additives in 1,2‐dimethoxyethane with 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether as a diluent. The solvated structure of Li + is regulated and the electrode‐electrolyte interfaces are elaborately designed, which effectively inhibits the growth of lithium dendrites and protects cathode structure from being damaged. Finally, the Li||LiNi 0.8 Mn 0.1 Co 0.1 O 2 (Li||NCM811) cell using modified electrolyte exhibits outstanding cycling stability at 5C, 4.4 V, delivering 71.3% capacity retention after 1000 cycles. The assembled 2 Ah Li||NCM811 pouch cell delivers a high energy density of 350 Wh kg −1 and a high‐capacity retention of 93.7% after 70 cycles at 1C, 4.4 V.